Desktop color copier which includes a revolving type developing device

ABSTRACT

A desktop color copier having a size which allows the copier to be placed on a stand when the copier is used. The desktop color copier includes a photoconductive drum for sequentially forming toner images of respective colors thereon, a charger for charging the photoconductive drum, an exposure device for exposing the charged photoconductive drum, a revolving type developing device for forming color toner images on the photoconductive drum, an image transferring devices which includes an intermediate transfer belt to which the color toner images are sequentially transferred one on top of the other, and a fixing device for fixing the color toner images on a sheet of paper. The desktop color copier includes a single paper feed tray which is located under the transferring devices.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention is a continuation-in-part of U.S. application Ser.No. 08/215,608, filed Mar. 22, 1994 now U.S. Pat. No. 5,600,445, whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a color copier. More particularly, theinvention is concerned with a desktop color copier which can be used ona stand.

2. Description of the Related Art

It is desired to provide a space saving office device such as a copier,printer, or facsimile machine in order to minimize the amount of spaceoccupied by the office device. Considering transportation of the officedevice, it is also desired to construct the office device to havemeasurements which are smaller than the entrance of an elevator.

In order to satisfy the aforementioned demand, a desktop black and whitecopier has been put on the market. The desktop copier usually can beused on a stand and therefore the measurements, especially the height,are small. It is desirable for the total height of the desktop copierwhich is on the stand to be about 950 mm in view of the operation of thecopier. It is also desirable that a desktop color copier be put on themarket in order to satisfy demand. However, it is very difficult tomanufacture a desktop color copier because color image forming devices,at least three developing devices and an intermediate transfer devicewhich are not necessary for the black and white copier are necessary fora color copier, and therefore it is very difficult to provide a smalldesktop color copier. As proof of that, a desktop color copier has notbeen put on the market.

Further, the color copier has two or more paper feed devices since thecolor copier has more functions than the white and black copier. As aresult, the color copier becomes large-size and therefore the desktopcolor copier cannot be built.

In view of improvement of efficiency of design and cost-efficiency, itis desired to reduce the size of the color copier. Namely, in order toimprove efficiency of design and reduce the cost, it is essential to usecommon parts among different copiers. In order to use common parts, itis essential to use a common frame which determines the size of thecopier for both the black and white copier and the color copier.

However, image forming devices, at least three developing devices and anintermediate transfer device, which are not necessary for the black andwhite copier are necessary for the color copier and therefore, the sizeof the color copier is larger than that of the black and white copier.As a result, it is impossible to use common parts, especially a commonframe, for both the color copier and the black and white copier.

SUMMARY OF THE INVENTION

Accordingly, one object of this invention is to provide a novel colorcopier which can solve the aforementioned drawbacks. A further object ofthe present invention is to provide a color copier which can be used ona stand.

In order to achieve the above-mentioned objects, according to thepresent invention, a color image forming apparatus for forming a tonerimage on a sheet of paper includes an image carrier for sequentiallyforming toner images of respective colors thereon, a charger forcharging the image carrier, an exposing device for exposing the chargedcarrier and forming electrostatic latent images of respective colors onthe image carrier, and a revolving type developing device which isrotatively supported in the color image forming apparatus.

The revolving type developing device includes a plurality of colordeveloping devices, each of which includes a developing unit fordeveloping a toner image on the image carrier when the developing unitfaces the image carrier and a toner supply unit for supplying toner tothe developing unit. The external shape of the revolving type developingdevice is a cylinder.

The color image forming apparatus further includes an intermediatetransfer belt to which the toner images are sequentially transferred oneabove the other, a primary transferring charger for sequentiallytransferring the toner images from the image carrier to the intermediatetransfer belt, thereby forming a composite toner image on theintermediate transfer belt, at least one paper feed tray for storingsheets of paper and feeding a sheet of paper. There is also a secondaryimage transferring charger for transferring the composite toner imagefrom the intermediate transfer belt to the sheet of paper which is fedfrom the paper feed tray, and a fixing device for fixing the toner imageon the sheet of paper. The color image forming apparatus is usually usedwhen the color image forming apparatus is on a stand.

Other objects and aspects of the present invention will become apparentherein.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic sectional view showing a digital color copierembodying the present invention;

FIG. 2 is a block schematic diagram showing a control unit of thedigital color copier embodying the present invention;

FIG. 3A is a perspective view showing the general construction of adeveloping device of the present invention including a black developingcartridge 506;

FIG. 3B is a perspective view from the rear showing the black tonercartridge 506;

FIGS. 4A-4D illustrate the rotation of the developing device and themanner of transferring toner from the black toner cartridge 506 to thehopper 507;

FIG. 5 is a schematic sectional view showing the digital color copierembodying the present invention;

FIG. 6 is a partial perspective view of the digital copier embodying thepresent intention;

FIG. 7 is a schematic perspective view of the digital color copierembodying the present invention; and

FIG. 8 is a schematic sectional view of the digital color copier whichis on a stand embodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Description of the Digital Color Copier

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, and moreparticularly to FIG. 1 thereof, a digital color copier embodying thepresent invention is shown. As shown, the digital color copier has ascanner unit 100 which scans and image on a document, control unit 200which has a electric circuit such as a control board having amicroprocessor and so on, and a printer unit 300 which forms a tonerimage on a sheet of paper.

The scanner unit 100 includes a first device 31 which irradiates lightonto the document, a second device 35 which reflects light from thedocument to a lens 33 and a charge coupled device 35.

The printer unit 300 has a rotatable photoconductive drum 1. The printerunit 300 also includes a charger 3 which charges the photoconductivedrum 1, a revolving type developing device 5, an intermediate transferbelt 7 which bears a composite toner image, a primary transfer charger 9which transfers the toner image on the photoconductive drum 1 to theintermediate transfer belt 7, a belt cleaning device 11 which cleansresidual toner on the intermediate transfer belt 7 and a cleaning device13 which cleans residual toner on the photoconductive drum 1. Therevolving type developing device is made up of a yellow developing unit508, a magenta developing unit 509, a cyan developing unit 510 and ablack developing unit 511 which are mounted on a movable support 512. InFIG. 1, a toner supply unit which is disposed in front of the revolvingtype developing device 5 with respect to the operating position of thecopier is not illustrated.

The printer unit 300 further includes a single paper feed tray 15 whichstores sheets of paper, a manual paper feed tray 16, a first pick uproller 17 which feeds a sheet of paper from the paper feed tray 15, asecond pick up roller 18 which feeds a sheet of paper from the manualpaper feed tray 16, a pair of paper transport rollers 19 which transportthe sheet of paper, a pair of resister rollers 21 which feed the sheetof paper to a transfer position so as to synchronize the composite tonerimage on the intermediate transfer belt 7 and the sheet of paper, asecondary transfer charger 23 which transfers a toner image on theintermediate transfer belt 7 to the sheet of paper, a paper transportbelt 25 and a fixing device 26 which includes a pressure roller 27 and afixing roller 29 to fix the toner image on the sheet of paper. Theprinter unit 300 further includes a laser exposing device 37 whichirradiates the photoconductive drum 1 with laser light in response to animage signal produced in accordance with the image detected by thecharge coupled device 35.

As shown in FIG. 2, the control unit 200 includes an interface 39 whichconnects the digital copier to a host computer, a printer processingboard 41 which converts print data in a page description language formatreceived from the interface 39 to raster data, an interface 43 whichconnects the digital color copier to a public line such as an ISDN, acolor facsimile processing board 45 which expands or decompresses datain a specified compression format received from the interface 43 andcompresses image data read by the scanner unit 100 into a specifiedformat, and an interface 49 which sends data to the interface 47 andreceives data from the interface 47.

Next, a description is set forth for functions of each section of thedigital color copier as shown in FIG. 1.

Read Operation of The Scanner Unit

The document to be scanned is placed on a platen glass 2 with a surfaceto be copied facing downward. The lens 33 forms an image of the documentin a reduced size on the charge coupled device 35. The charge coupleddevice 35 has a red image pickup section, a green image pickup sectionand a blue image pickup section.

An illuminating lamp and a first mirror are mounted on the first device31, while a second mirror and a third mirror are mounted on the seconddevice 35. The first and second devices 31 and 35 move as a scanningoperation is being performed. When scanning the image on the document,the first device 31 and the second device 35 are driven at the scanningspeeds Vsub and Vsub/2, respectively for scanning from the left edge tothe right edge by a scanning motor.

Operation of the Printer Unit

When an image forming cycle is started, the photoconductive drum 1 isrotated counterclockwise and the intermediate transfer belt 7 is rotatedclockwise. Formation of a black toner image, a cyan toner image, amagenta toner image and a yellow toner image is executed successively inassociation with rotation of the intermediate transfer belt 7. Finallythe toner images are superimposed in the order of Black, Cyan, Magentaand Yellow on the intermediate transfer belt 7 to form a composite tonerimage.

First, formation of the black image is executed as described below. Thecharger 3 charges the photoconductive drum 1 with a negative voltage of-700V. Then the laser exposing device 37 executes laser exposure inresponse to a black signal and subsequently an electrostatic latentimage of the black image is formed on the photoconductive drum 1.Recording signals for forming the electrostatic latent image areprovided from the scanner unit 100 in the copying mode, and from thecontrol unit 300 in a facsimile mode or a printer mode.

Toner in the black developing unit 511 is charged to a negative polaritywhen mixed and agitated with a ferrite carrier, and a developing rollerfor the black toner in the black developing unit 511 is biased to avoltage level where a negative DC voltage and an AC voltage aresuperimposed by a power source (not illustrated). As a result, the tonerdoes not adhere to an area of the photoconductive drum 1 where anelectric charge is still remaining but the toner does adhere to an areahaving no electric charge, namely in the area exposed to light.

Thus, when the toner image on the photoconductive drum 1 is rotatedcounterclockwise and reaches a position opposite to the transfer charger9, the toner image is transferred to the intermediate transfer belt 7which contacts the photoconductive drum 1 and is driven at the samespeed as that of the photoconductive drum 1. A small quantity ofresidual toner not transferred and remaining on the photoconductive drum1 is cleaned by the cleaning device 13.

The intermediate transfer belt 7 is made of material having anappropriate resistance value to maintain image carriage characteristicsfor a long time as is often requested in the printer mode. This featuremakes it possible for a toner image to be maintained for a long time;for instance for 20 minutes until formation of the next cyan tonerimage. The surface resistance value of the belt 7 is preferably 10⁹ to10¹⁰ Ω, and the volume resistance of the belt 7 is preferably 10¹⁰ to5×10¹¹ Ω·cm.

Then prior to exposure by a laser for forming a cyan image based on acyan signal, the developing unit 5 is rotated counterclockwise, and thecyan developing unit 510 is moved so that the cyan developing unit 510will face the photoconductive drum 1. Then a tip position of the blackvisual toner image previously formed is detected by a tip detectionsensor (not illustrated), and the data request signal for requestingtransfer of recorded cyan image data in a specified time is again issuedto the scanner unit 100 in the copying mode and to the control unit 200in the facsimile mode and the printer mode. This request signal isissued simultaneously when the tip detection sensor detects a blacktoner mark image for registration provided a little ahead of theeffective black image in the previous process and the effective blackimage. Also, a system in which a permanent mark is put in place of theblack toner mark on the intermediate transfer belt 7 may be used.

If a cyan signal is received in precise synchronism with the requestsignal, exposure of a cyan image, development, and primary transfer areexecuted. Further, accurate color print section alignment can beexecuted against the original black image; namely the cyan image iscorrectly superimposed on the black image on the intermediate transferbelt 7. Thus, when the photoconductive drum 1 is exposed to light whichcorresponds to the cyan image, electric charge in proportion to aquantity of light of the cyan image is removed from the photoconductivedrum 1 which was initially uniformly charged, thus forming theelectrostatic latent image.

Cyan toner in the developing unit 510 is charged to a negative polarity,and the cyan development roller in the developing unit is held incontact with the photoconductive drum 1 and is biased to a voltagesimilar to that in the black developing unit. As a result, the tonerdoes not adhere to a section of the photoconductive drum 1 whereelectric charge remains while cyan toner adheres to a section exposed tolight corresponding to the cyan image signal, and a cyan toner imagecorresponding to the electrostatic latent image is formed.

Similarly a magenta image and a yellow image are superimposed on theblack and cyan toner images. A full-color image formed on theintermediate transfer belt 7 which has rotated at least four times asdescribed above is rotated and transferred to a position of the transfercharger 23.

On the other hand, at a timing when formation of an image is started, asheet of paper is fed from one of the paper feed tray 15 and the manualpaper feed tray 16, and reaches a nip of the resister rollers 21. Theresister rollers 21 are driven so that a tip of the sheet of papercoincides with a tip of the image when a tip of a toner image on theintermediate transfer belt 7 is passing by the transfer charger 23, thusperforming registration alignment between the sheet of paper and theimage.

Thus the sheet of paper superimposed on an image on the intermediatetransfer belt 7 passes under the secondary transfer charger 23 connectedto a positive voltage power source (not illustrated). Then most of thetoner image is transferred to the sheet of paper. When the sheet ofpaper passes over a discharging brush 24, the sheet of paper isdischarged, and most of the absorbing force between the intermediatetransfer belt 7 and sheet of paper disappears. Then the tare weight ofthe sheet of paper becomes larger than the absorbing force when thesheet of paper is separated from the intermediate transfer belt 7.

The sheet of paper with a toner image thereon is transferred by thetransport belt 25 to a fixing device 26. Heat and pressure are appliedto the sheet of paper at a nip between the pressure roller 27 and thefixing roller 29 and the toner image is fixed on the sheet of paper. Thesheet of paper is discharge from the copier and is stacked on a paperdischarge tray.

Revolving Type Developing Device

FIG. 3A shows a revolving type developing device. Referring to FIG. 3A,the revolving type developing device 5 which includes a toner supplydevice 501 and a developing tank 502 in a body is rotatively supportedon the printer unit 300. The toner supply device 501 includes a yellowtoner cartridge 503, a magenta toner cartridge 504, a cyan tonercartridge 505, and a black toner hopper 507. The developing tank 502includes a yellow developing tank, a magenta developing tank, a cyandeveloping tank, and a black developing tank, each of which includes adeveloping roller, an agitator and so on. The yellow developing tank,the magenta developing tank, the cyan developing tank and the blackdeveloping tank face the yellow toner cartridge 503, the magenta tonercartridge 504, the cyan toner cartridge 504 and the black toner hopper507, respectively.

There is a black toner cartridge 506 which is a cylindrical cartridgehave a length which runs from the toner supply device 501 to the end ofthe developing tank or unit 502 as shown in FIG. 3B. This tonercartridge revolves around the axis of rotation of the toner supplydevice 501. In this embodiment, the black toner cartridge 506 is locatedat the axis of rotation of the toner supply device 501, although it ispossible for the black toner cartridge 506 to be located away from theaxis of rotation of the toner supply device 501. The toner cartridgesare each made of a plastic or plastic-like substance, are purchased fullof toner, and disposable. Alternatively, the toner cartridges arerefillable.

FIG. 3B is a view from the rear of the black toner cartridge 506. Therear of the cartridge 506 includes an opening 520 through which thecartridge is filled at the factory. Once filled, this opening 520 issealed. A spiral groove is formed inside the black toner cartridge 506.When the black toner cartridge 506 rotates, black toner is supplied tothe black toner hopper 507 through an opening 522, and then black toneris supplied from the black toner hopper 507 to the black tonerdeveloping tank. The cartridge 506 includes a latching mechanism 524which connects the cartridge 506 to the body of the toner supply device501. The capacity of the black toner cartridge is greater than that ofthe other toner cartridges.

As mentioned above, when development for the black toner image isexecuted, the black developing tank faces the photoconductive drum 1 byrotating the revolving type developing device 5. When development forthe yellow toner image is executed, the revolving type developing device5 rotates and then the yellow developing tank faces the photoconductivedrum 1. The operation of the magenta toner image and for the cyan tonerimage is as same as that of the yellow toner image.

According to the present embodiment, a body of the revolving typedeveloping device is small, since the toner supply device 501 and thedeveloping tank 502 are in the body and therefore, it is not necessaryto provide a toner transport device between the toner supply device andthe developing tank which is exterior to the developing tank. As aresult, the digital color copier or other color printing device becomessmall.

FIGS. 4A-4D illustrate the revolving of the toner supply device 501which causes black toner to be transferred from the black tonercartridge 506 to the black toner hopper 507. FIG. 4A illustrates thedeveloping device with the black toner developer located at thedeveloping position. In this figure, there is illustrated the blacktoner cartridge 506 in the center thereof having an opening 522 and atriangular ridge 526. The opening 522 of the black toner cartridge 506at this time is closed by a door 530. In the illustrated embodiment, thedoor 530 is opened and closed by gravity. As an alternative, the door isoperated using either a mechanical or electromechanical device. In thisposition, black toner does not commute between the black toner hopper507 and the black toner cartridge 506.

FIG. 4B illustrates the cyan toner cartridge 505 in the developingposition after the toner supply device 501 rotates one quarter of arevolution counter-clockwise. In this position, the door 530 whichcloses the opening 522 remains closed.

FIG. 4C illustrates the magenta toner cartridge 504 in the developingposition. In this figure, the door 530 has fallen open due to gravity.Once the door is open, toner within the cartridge 506 flows through theopening 522 and into the black toner hopper 507.

FIG. 4D illustrates the toner supply device 501 which has been rotatedso that the yellow toner cartridge 503 is in the developing position. Inthis position, the door 530 remains open due to gravity and black tonercontinues to flow from the black toner cartridge 506 to the black tonerhopper 507. In this figure, the triangular ridge 526 guides the blacktoner through the opening 522. The triangular ridge 526 extends from thefront of the cartridge 506 to the point of the cartridge 506 where thespiral ends or alternatively, to a point of the cartridge 506 before thespiral starts.

After one more quarter of a revolution, the toner supply device 501returns to the position illustrated in FIG. 4A and the door 530 isclosed due to gravity and toner cannot commute between the cartridge 506and the hopper 507.

FIG. 5 shows a color digital copier in which the toner supply device isincorporated in the copier. In the present embodiment, in order toreduce the size of the digital color copier the diameter of the tonersupply device 501 is larger than that of the developing tank 502.

Size of the Copier

As mentioned above, it is desirable that the height of the desktop typecopier while on a stand be about 950 mm. The height of a conventionaldesktop type black and white copier is usually about 570 mm, andtherefore the height of the stand is about 380 mm (950 mm minus 570 mm),950 mm being the desired height. It is desirable that measurements ofthe digital color copier be the same as that of the desktop type blackand white copier in order to promote the efficiency of design and to cutcost by using a common frame for the color copier and the black andwhite copier. Further in view of the carriage of the copier, it isnecessary to provide the digital color copier with measurements whichare smaller than the entrance of an elevator.

From the aforementioned viewpoints, the measurements of the digitalcolor copier of the present embodiment are as follows: the width is 620mm, the depth is 680 mm, and the height is 592 mm as shown in FIG. 7. Itis allowable if each of the measurements changes within ±30 mm from theactual dimension of the digital color copier.

Sizes of Photoconductive Drum and Intermediate Transfer Belt

The intermediate transfer belt with respect to the moving direction ofthe belt must be longer than the length of the maximum size of the sheetof paper which can be used by the digital color copier of the presentembodiment, since the intermediate transfer belt must bear an entiretoner image which corresponds to a document which is to be copied. Themaximum size of the sheet of paper which can be used by the color copieris A3 size (210 mm×420 mm) or DLT (Double Letter) size (11 inch×17inch=279.5 mm×432 mm). Further, it is necessary that the length of theintermediate transfer belt with respect to the moving direction of thebelt be an integral number of times as the length of the photoconductivedrum with respect to the moving direction of the drum (i.e., the outercircumference of the photoconductive drum), since it is necessary forthe tip of the toner image on the photoconductive drum to coincide withthe intermediate transfer belt. In order to provide a small colorcopier, it is necessary to reduce the length of the photoconductive drumand that of the intermediate transfer belt. However, since the length ofthe transfer belt must be an integral number of times as that of thephotoconductive drum, if the length of the photoconductive drum becomeslong, that of the intermediate transfer belt also becomes long. As aresult, the color copier becomes large.

The inventors have examined a possibility of adopting various sizes ofphotoconductive drums. As a result of the examination, it turned outthat the maximum size of the photoconductive drum had to be .oslashed.90 (90 mm in diameter) in order to satisfy the aforementionedcondition and to satisfy the measurements of the copier being 680±30mm×620±30 mm×592±30 mm. In this condition, the length of theintermediate transfer belt was twice that of the photoconductive drum.

On the other hand, it is necessary to locate a plurality of processdevices, such as a charger, a revolving type developing device, anintermediate transfer belt, and a cleaning device around aphotoconductive drum. The inventors also examined the minimum size ofthe photoconductive drum, which could accommodate the process devices.As a result of the examination, it turned out that the minimum size ofthe photoconductive drum had to be .o slashed.30 (30 mm in diameter). Ifthe size of the photoconductive drum was less than 30 mm, it was notpossible to locate the process devices around the photoconductive drum.In this condition, the length of the intermediate transfer belt was fiveor six times that of the photoconductive drum.

Cooling for Developing Device

In order to provide a desktop color copier, it is necessary to reducethe size of the copier. As a result, the developing device has to belocated close to the fixing device such as approximately 10 mm.Therefore, toner in the developing device is hardened by means of heatfrom the fixing device.

In the present embodiment, cooling air flows in a direction indicated byarrows as shown in FIG. 6. Referring to FIG. 6, fans 51-55 are providedaround the fixing device 26. The fan 51 which is an intake fan and thefan 2 which is an exhaust fan create an air flow between the developingdevice 5 and the fixing device 26 and therefore heat from the fixingdevice 26 is not transmitted to the developing device 5. Further, thefan 53 which is an intake fan and the fans 54 and 55 which are exhaustfans create air flow above the fixing device 26 which prevents heat fromgathering above the fixing device 5 and lowers the temperature of thefixing device 5.

System Configuration of Desktop Color Copier

FIG. 8 shows a desktop digital color copier which is on a stand.Referring to FIG. 8, the desktop color copier 57 is on a paper feed bank59 which is used as the stand. Alternatively, the stand may be a simplesupporting stand without paper feeding capabilities. In the presentembodiment, the paper feed tray 15 of FIG. 1 is replaced with a duplexpaper feed tray 61. A sheet of paper is fed from a manual paper feedtray 16 or one of paper feed trays 63-67 to the transfer charger 23where a toner image on the intermediate transfer belt 7 is transferredto the sheet of paper. After the transferring operation, the sheet ofpaper is transported to the duplex paper feed tray 61 via the fixingdevice 26. The sheet of paper is stacked in the duplex paper feed tray61 with the image side facing upward. Then the sheet of paper is fedfrom the duplex paper feed tray 61 toward the secondary transferringcharger 23 where a toner image on the intermediate transfer belt 7 istransferred to the other side on the sheet of paper.

In the embodiment illustrated in FIG. 8, the height H of the digitalcolor copier is 950 nm.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A color image forming apparatus for forming atoner image on a sheet of paper, comprising:an image carrier forsequentially forming toner images of respective colors thereon; acharger for charging said image carrier; an exposure device for exposingsaid image carrier which has been charged and forming electrostaticlatent images of respective colors on said image carrier; a revolvingtype developing device which is rotatively supported in said color imageforming apparatus, including a plurality of color developing devices,each of which includes a developing unit for developing a toner image onsaid image carrier when said developing unit faces said image carrierand a toner supply unit for supplying toner to said developing unit,wherein an external shape of said revolving type developing device is acylinder; an intermediate transfer belt to which said toner images aresequentially transferred on top of previously transferred toner images;a primary transferring charger for sequentially transferring said tonerimages from said image carrier to said intermediate transfer belt toform a composite toner image on said intermediate transfer belt; atleast one paper feed tray for storing sheets of paper and feeding thesheets of paper one at a time; a secondary image transferring chargerfor transferring said composite toner image from said intermediatetransfer belt to one of the sheets of paper; and a fixing device forfixing said toner image on said sheet of paper, wherein the revolvingtype developing device includes a cylindrical black toner cartridgedisposed along an axis of rotation of the revolving type developingdevice.
 2. A color image forming apparatus as claimed in claim 1,wherein said image forming apparatus is a color copier.
 3. A color imageforming apparatus as claimed in claim 2, wherein said at least one paperfeed tray is a single paper feed tray.
 4. A color image formingapparatus as claimed in claim 3, wherein said paper feed tray is locatedunder said image carrier, said revolving type developing device, saidintermediate transfer belt, said primary transfer charger, saidsecondary transfer charger, and said fixing device.
 5. A color imageforming apparatus as claimed in claim 2, wherein said color imageforming apparatus is a digital color copier.
 6. A color image formingapparatus as claimed in claim 1, wherein said image carrier is aphotoconductive drum having a diameter from 30 mm to 90 mm.
 7. A colorimage forming apparatus as claimed in claim 3, wherein a length of saidintermediate transfer belt with respect to the moving direction of saidbelt is an integral number of times a circumference of saidphotoconductive drum.
 8. A color image forming apparatus as claimed inclaim 7, further comprising a stand for supporting the image formingapparatus, said stand having a plurality of paper feed trays from whichsaid one of the sheets of paper is fed, wherein said at least one paperfeed tray is a duplex paper feed tray.
 9. A color image formingapparatus as claimed in claim 1, wherein said revolving type developingdevice is located within 10 mm from said fixing device.
 10. A colorimage forming apparatus as claimed in claim 8, further comprising:fanswhich create an air flow between said revolving type developing deviceand said fixing device for cooling said revolving type developingdevice.
 11. A color image forming device as claimed in claim 1, whereinsaid plurality of color developing devices include cyan, magenta, andyellow developing devices, each having toner cartridges which rotatewith the revolving type developing device.
 12. A color image formingdevice as claimed in claim 11, wherein the black toner cartridge has adoor which opens and closes by a force due to gravity as the revolvingtype developing device revolves such that toner is permitted to flowfrom the black toner cartridge when the door is open and toner is notpermitted to flow between the black toner cartridge and a correspondingdeveloping unit of the developing device when the door is closed.
 13. Acolor image forming apparatus according to claim 1, further comprising:astand for supporting the color image forming apparatus.
 14. A colorimage forming apparatus according to claim 13, wherein a height of thecolor image forming apparatus when being supported by the stand is lessthan or equal to 950 mm.
 15. A color image forming apparatus accordingto claim 13, wherein a height of the stand is at least 380 mm.